Farms of the Future: Bio-Oil, Biochar from Biomass

Jul 22, 2011

Rural landscapes of the future might have pyrolysis plants instead of grain elevators on every horizon —processing centers where farmers would bring bulky crops such as switchgrass to be made into crude oil.

Those pyrolysis plants would pass that crude “bio-oil” on to refineries elsewhere to be made into drop-in fuels and industrial chemicals; they would capture and use for their own energy needs a byproduct called syngas made up of hydrogen, carbon monoxide and perhaps carbon dioxide; and they would send farmers away with an important byproduct called biochar that could go back on the land to help rebuild damaged soils, sequester carbon and alter greenhouse gas emissions.

Sound futuristic? It’s also a current research focus at South Dakota State University.

A major new study by researchers at the university working with a U.S. Department of Agriculture colleague explores how to get the most from such a production system. The USDA is funding the project with a grant of $1 million — $200,000 annually for the next five years — to help scientists design a feedstock production system for optimum energy production of “bio-oil,” and also to explore the possible ecological benefits from the use of biochar.

The grant was selected by the USDA’s National Institute of Food and Agriculture’s flagship competitive grants program called AFRI, or the Agriculture and Food Research Initiative. It was selected in the sustainable bioenergy challenge area. Typically fewer than 10 percent of proposals are funded, with awards based on external peer reviews of a proposal’s scientific merit.

“We’re looking at this from a whole system approach, and we’re looking at various components in this whole system,” said SDSU professor Tom Schumacher, the project director. “Historically, the distributive nature of crop production gave rise to a network of grain elevators to separate and coordinate the flow of grain to the processing industry. A network of rail lines added new infrastructure to improve efficiency. For lignocellulosic feedstocks, a corollary to the grain elevator would be a collection point that would be within 10 to 30 miles of production fields.”

Those collection points wouldn’t be for long-term storage, but to receive, sort and pre-process or process feedstocks using pyrolysis to break them down into bio-oil, syngas and biochar. Making crude bio-oil would have the effect of densifying the material to a liquid form that is easier to transport for further processing. Meanwhile, the biochar would likely be used in fields in the service area of the pyrolysis plant.

Pyrolysis is a process that uses elevated temperatures in the absence of oxygen to break down organic materials. The SDSU study will more specifically use a technique called microwave pyrolysis that heats the feedstock by exciting the individual molecules, making it very accurate and easy to control.

Schumacher’s co-principal investigators on the project include professors Sharon Clay, David Clay, Ronald Gelderman, and Douglas Malo and research associate Rajesh Chintala, all of SDSU’s department of plant science; professor Jim Julson and assistant professor Lin Wei in the department of agricultural and biosystems engineering; and supervisory soil scientist Sharon Papiernik of the USDA Agricultural Research Service’s North Central Agricultural Research Laboratory in Brookings, S.D.

Process engineers and soil scientists are collaborating in the research project to learn what happens to bio-oil and biochar production when they vary the pyrolysis processing parameters.

Researchers hypothesize that biochar has different physical and chemical properties depending on the feedstock and the way it is processed. That could affect its usefulness as a soil amendment. They’ll examine the characteristics of biochar from three feedstocks: corn stover, switchgrass and woody biomass.

“There’s a lot that’s unknown about specific types of biochar. There is no single characteristic that can be used to evaluate the effectiveness of biochars,” Schumacher said.

Biochar’s pH and other characteristics can vary widely depending on what feedstock and process was used to produce it, Schumacher said. That could make biochar beneficial to the environment, neutral, or possibly even harmful, depending on its characteristics. But scientists are excited about the possibility of finding beneficial uses for a consistent, well-characterized biochar product.

“In particular, we’re interested in it as a soil amendment for soils that have erosion and degradation problems, with the idea that the biochar could be used to improve those soils,” Schumacher said. “There’s some indication that some biochars can improve water-holding capacity. Biochar also interacts with soil nutrients, holding them, keeping them from leaching. At least there’s some indication that some biochars will do it — others may not.”

Microbial activity may improve with the use of some particular kinds of biochar. And importantly, biochar is thought to have the ability to tie up carbon for centuries or even for thousands of years, meaning it could be used as a tool to slow global warming.

“We also want to explore the effects of the biochar on herbicide absorption and leaching, and how it interacts with herbicides. Does it tie it up so it’s not as effective? Does it make it more active? It may have some potential to be used in certain environmentally sensitive areas as a filter, if you would, that would tie up certain chemicals or keep them from moving,” said professor Jim Julson in SDSU’s Department of Agricultural and Biosystems Engineering.

Some types of biochar might also play a similar role in helping to tie up phosphorus to prevent it from washing out of a field with runoff — an important consideration for managing nutrients such as manure.

SDSU researchers will do laboratory and greenhouse studies, and ultimately field studies as well. The work will characterize different types of biochar in order to build a better picture of how a pyrolysis treatment plant could produce both bio-oil and biochar, in addition to the syngas that would be used for helping to supply the plant’s energy needs/